What happened

Sangamo Therapeutics (NASDAQ:SGMO) closed down 10.5% while bluebird bio (NASDAQ:BLUE) slipped 4.8% after competitor Global Blood Therapeutics (NASDAQ:GBT) reported positive data for its sickle cell disease drug, voxelotor.

So what

In the part A of Global Blood's phase 3 study, 58% of patients taking the higher dose of voxelotor reached the pre-defined goal of a 1 g/dL increase in hemoglobin, while 38% of the patients taking the lower dose reached the goal, compared to just 9% of patients taking placebo.

But that's not even the worse news for Sangamo and Bluebird.

The data for the higher dose was so good -- Global Blood was shooting for a 35% response rate -- that the company is now in discussions with the Food and Drug Administration to potentially accelerate the approval rather than waiting for part B of the study before applying.

Sickled and normal red blood cells.

Image source: Getty Images.

Now what

The bad news is that an accelerated approval could extend Global Blood's lead over Sangamo and Bluebird. Sangamo's gene editing therapy for sickle cell disease hasn't entered the clinic yet, although treatment for a related disease called beta-thalassemia is in a phase 1/2 trial. Bluebird's gene therapy, LentiGlobin, is in phase 2 development for sickle cell disease.

The good news for Sangamo and Bluebird is that voxelotor appears to be far from a cure with just 58% of patients responding. Given the higher risks of editing patients' DNA, both Sangamo's and Bluebird's therapies are most likely going to end up treating the sickest sickle cell patients, so there may not be much of an overlap with the patients that voxelotor is likely to help.

Today's downturn could end up being a buying opportunity, just keep in mind that both therapies are a ways away from being approved for sickle cell disease.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Bluebird Bio. The Motley Fool has a disclosure policy.